1. Field of the Invention
The present invention relates to a battery charger, more specifically to a battery charger having a rotary AC plug which can be accommodated in a case of the main body.
2. Description of Related Art
In recent years, various types of portable machines including digital video cameras, digital still cameras and the like are well accepted by many generations and find wide applications. Power supplies for such portable machines are mostly batteries. In particular, in light of advanced battery technology and ever increasing users' conscious to recycling, many portable machines are designed to operate on rechargeable batteries (for example, lithium ion batteries).
In response to increased demands for such rechargeable batteries, many battery chargers for charging batteries by using an AC power supply are on the market.
There are conventional battery chargers such as one capable of accommodating an AC plug within the main body of the charger (see Patent Document 1) and one having contact members with which the AC plug and the main body of the charger make contact (see Patent Document 2). In the Patent Document 1, the AC plug rotates about rotary shafts extending through a support member of the AC plug for supporting a pair of electrically conductive blades and projects at 90 degrees with respect to the main body of the charger, thereby enabling the user to insert into a wall outlet of an AC power supply. Such rotation is oriented in the direction of the plate surface of the pair of conductive blades.
On the contrary, there is another type in which an AC plug is similarly constructed to project at 90 degrees from the charger main body by rotating about rotary shafts passing through a support portion for supporting the conductive blade, but rotating in the direction perpendicular to the plate surface of the pair of conductive blades (so-called lateral rotary type). In this specification, the mode in which the AC plug rotates laterally is referred to as the “lateral rotation”.
An example of conventional battery chargers belonging to such type is shown in FIGS. 7A and 7B and FIG. 8. FIG. 7A shows the front view and FIG. 7B shows the plan view in the condition where the AC plug to be inserted into a wall outlet of the AC power supply is projecting at about 90 degrees from the case of the battery charger.
FIG. 7A shows the condition where the AC plug 51 having a pair of conductive blades 52, AC plug rotary shafts 53, and contact portions 54 for making electrical contact with the aforementioned conductive blades is projecting from a case 50 of the battery charger at substantially right angle. The AC plug 51 is able to rotate laterally about the AC plug rotary shafts 53 by about 90 degrees in the direction of an arrow d. Because of such rotation, it is constructed so that the AC plug 51 can be accommodated within the case 50. Disposed on the surface of the AC plug rotary shaft 53 are the contact portions 54 which are electrically connected to the respective conductive blades 52.
The aforementioned contact portions 54 are respectively disposed in such a manner to oppose to each other with the center point of the rotary shaft 53 of the AC plug between them near the outer circumferential surface of the circular rotary shaft 53 of the AC plug. Additionally, the contact portions 54 are contacting with respective conductive spring terminals 55 for making electrical connection therebetween under the condition as shown in FIG. 7A.
When the AC plug 51 is rotated at about 90 degrees in the direction of the arrow d, the portions of the rotary shaft 53 of the AC plug also rotate in the direction of the arrow d and the contact portions 54 disposed on the surface of the rotary shaft 53 of the AC plug also rotate in the direction of the arrow d, thereby separating the contact portions 54 from the respective conductive spring terminals 55 so as to maintain a constant distance.
The contacting condition between the contact portions 54 and the conductive spring terminals 55 is more clearly shown in FIG. 7B. Also formed is a cavity portion 56 acting as a space for accommodating the conductive blades 52 when the AC plug 51 is laterally rotated at about 90 degrees in the direction of the arrow d in FIG. 7A.
FIG. 8 shows the aforementioned AC plug 51 under the condition as shown in FIGS. 7A and 7B, i.e., a perspective view of the neighboring portion of the AC plug 51 when the conductive blades 52 are projecting at substantially right angle with respect to the case 50.
In this type of battery charger, as apparent by making reference particularly to FIG. 7B, the contact portions 54 for respective poles are disposed on the surface of the rotary shaft 53 of the AC plug at the same side.    [Patent Document 1] Japanese Patent Application Publication No.HEI 6-38388    [Patent Document 2] Japanese Utility Model Application Publication No. HEI 5-88152